Black's e-pawn is weak in the static sense, but it
lends valuable support to his knight. If White takes,
Black's weak e-pawn transforms into a passed d-pawn.
But Black should be reluctant to trade the knight
other than on the d5 square.

White now has:

B11. 19. Nxd5
B12. 19. Qg4

19. Rc1 Qd7 likely transposes to one of these variations.

B11. 19. Nxd5

19...exd5 20. Re1 Qd7 and Black is okay.

B12. 19. Qg4

19...Bf6 20. Rac1 Qd7

Choices for White:

B121. 21. Bxf6
B122. 21. Nxd5

B121. 21. Bxf6

21...Nxf6 (21...Rxf6 22. Nxd5 Qxd5 23. Rfd1 Qf5
24. Qd4 and White is in control) and with the knight
soon heading back to the d5 square, Black seems fine.